Incandescent lamp



June 28, 1932. E; R. MORTON ET AL INCANDESCENT LAMP Filed Aug. 7. 1929E. P. MORTON h! M STOLLE/P mk w A TTO/PNEY Patented June 28, 1932 UNITEDSTATES- PATENT OFFICE IDHUND B. MOB'10N, O1 NEW YORK, N. Y., AND HUGH I.STOLDER, OF MOUNTAIN LAKES, NEW JERSEY, ASSIGNOBS TO BELL TELEPHONELABORATORIES, INCORPO- RATED, OF NEW YORK, N. Y A CORPORATION OF NEWYORK mcsmmscmrr rm Application mea' August 7, 1929. Serial in. 384,032.

This invention relates to incandescent lamps and more particularly, toincandescent electric lamps operated by alternating curren 5 The objectof this invention is an incandescent lamp in which the energy operatingthe lamp produces less variation in emitted light than is usual withpreviously known lamps. Under favorable conditions, the variation in theemitted light is so reduced that the light is ractically constant. p

t is well known that the luminosity and color of the light emitted by anincandescent solid varies with the temperature of the sur- 16 face ofthe solid. In the commercial incandescent lamp operated on alternatingcurrent, the luminosity and color vary with the variation in the currentbut due to the persistence of vision, this variation I is normally notnoticed by the eye. On certain commercial systems, however, thefrequency is sufliciently low that the varlation in the light isobjectionable.

Many light sensitive device such as the photoelectric cell, aresuflicien y sensitive to detect the variation in luminosity of acommercial incandescent lamp when operated on alternating current. Thesedevices are also usually sensitive to changes in the color of the li htfalling on the device. Thus, if an incandescent lam operated onalternating current excites a p otoelectric cell, the output current ofthe cell will. have a component which varies with the variation in thelight.

this component will produce an un esirable tone in the sound.

This invention provides an incandescent lam in which the variation ofthe energy operatmg the lamp produces a variation in the light. Thus,when this lamp is used, for example, on alternatin current circuits oflow frequency the variation of the light is not percep ible to the eye.Also, the undesired compone t in the output circuit of a photoelectriccell excited by a lamp constructed in accordance with this inventionwill be so reduced-that the tone produced is not objectionable. Afeature of this invention is the provision When the cell is used forreproducin sound,

of a filament havinga large heat storage capacity. The heat storagecapacity of the filament may be made large by increasing the ratiov ofthe mass of the filament to its surface. This invention contemplates theuse of a short heavy filament having a large mass in proportion to itssurface. The heat stored in the mass of the filament will be conductedto the surface during the time that the current is passing through itszero value and will aid in stabilizing the temperature of the surface.

Another feature of this invention resides in restricting the area of thesurface from which luminous energy is utilized to a small part of thetotal area. Thus the energy utilized is a small fraction of the totalenergy emitted. The temperature of the surface utilized. The remainderof the radiation is intercepted by the reflector and returned to thesurface of the filament, aiding in maintaining the surface of thefilament at a constant temperature. A plurality of co-axial, concentricshields may be used to more completely intercept and return theradiation.

The radiation falling on the reflector will tend to heat the reflectorand a ortion of this heat will be radiated to the fi ament, and aportion will be radiated from the surface of the reflector and lost. Toavoid extracting energy from the surface of the filament to supply thisheat loss, electric energy may be supplied to the reflector directly,either from a separate source, or by connecting the reflector in circuitwith the filament.

Referrin to the drawing Fig. 1 s ows an electrical incandescent lampmade in accordance with this invention;

. Fig. 2 isv atop view of the filamenfiand reflector ofthe lamp shown inFig. l}

nclosed in the bulb 1, of. any suitable shape, is a foot tube 2,supporting a filament 3. The filament 3 may be made of any suitablematerial, such as tungsten. The filament 3 is preferably short and oflarger diameter than the filaments generally used in electrical back onto the surface of the filament 3. In

incandescent lamps. The increased diameter will increase the ratio ofthe mass of the filament to its surface, and increase the ability of thefilament to retain heat. The heat retained in the filament will besupplied to the surface during the time in which the ener supplied tothe filament from the source 1 has fallen to a-small value, and will aidin maintaining constantithe temperature of the surface of the filament.

Partiallysurrounding the filament 3, is a reflector 4, of any suitableshape. For convenience of -description the reflector 4 has been shown asa cylinder. The reflector 4 may be of any material ca able of reflectingthe radiant energy emitted by the filament 3 a preferred form of thisinvention, a metallic reflector 4 is used. The reflector 4 is dividedlongitudinally by the slit 5 through which radiant energy emitted by thefilament 3 ma pass. The radiant energy passing throug the dihedral angledefined by the slit 5 has been termed the useful radiation in thisspecification. The unused radiation emitted by the filament 3. isintercepted by the reflector 4 and largely returned to the surface ofthe filament 3 and aids in maintainin temperature of the surface of t efilament 3. The radiant ener falling on the reflector 4 willbe partialla rbed and will raise the temperature of t e reflector 4. The increasedtemperature of the reflector ,4 will cause a portion of this energy tobe radiated from the outside of the reflector 4 and lost. To lessen thisloss of energy a second reflector 6 as shown in Fig. 3 may be placedoutside the reflector 4. The reflector 6 has a slit 7 correspondin tothe slit 5 in reflector 4 through which t e useful radiation may pass.

Another method of lessening the energy drawn from the filament 3 toraise the tem- V rature of the reflector 4, is to supply energ anexternal source to heat the re I 4 to the required temperature. Leadin-out wires 8 and Q maybe attached to-the ector 4, and ener may besupplied through these wires 8 an 9 to the reflector4. The'energ 7 maybe supplied from a separate source 16, or

the reflector 4 may be connected in the circuit which supplies energ tothe filament 3. If, more than one reflector be used-leadingout wires maybe attached to each reflector.

constant the Leases"? As shown in Fig. 3, energy may be supplied to thereflector 4 by means of leading-out wires 8 and 9, and to reflector 6 bymeans of leading-out wires 16 and 17.

A typical application of a lamp constructed in accordance with. thisinvention is shown in Fig. 4. The useful radiation from the lamp 1 fallson the lens 10, producing an image of the light emitting slit 5 focussedon the slit 11 in the opaque plate 12. The light passing through theslit ll falls on a lens 13, producing an image of the slit 1]. focussedon a film sound record 14. The light passing through the film soundrecord 14 falls on the photoelectric cell 15 and causes a variation ofthe output current of the hotoelectric cell 15 which is a reproduction othe variation of the film sound record 14.v

' What is claimed is:

1. In a lamp, a sealed envelope, a strai ht filament supported in saidenvelope, an a slitted electrically conductive reflector supported byelectrically conductive leading-1n wires in said envelope concentricallyand coaxially with respect to said filament to limit the li ht from saidfilament to a small dihedra angle having its. vertex parallel to theaxis of the filament.

2. In a lamp, a-sealed envelope, an incandescent body supported in saidenvelope, and a reflectin electrically conductive screen supported yelectrically conductive leadingin wires in said envelope to partiallysurround said body.

3. In a lamp, a sealed envelope, an incandescent body supported in saidenvelope and a plurality of reflectors supported in said envelopeconcentrically and coaxially with respect to said body, each of saidreflectors having a narrow light transmittin slit, said slits beingradially aligned with t e sxisiof 'said body.

4. In a lamp, a sealed envelope, an incandescent body supported in saidenvelope and a plurality of reflectors supported in said envelope eachreflector partially surrounding said body and combining with said otherreflectors to.limit the light from said body to a small dihedral anglehaving its vertex parallel to the axis of the body.

5.- In a lamp, a sealed envelope, an incubdescent body supported in saidenvelope, a reflecting screen purposed to carry elegtrical currents andsupported in said envelope to partially surround said body, and a secondreflecting screen supported in said envelope to partially surround saidbody and said first screen.

6. In a lamp, a sealed envelope, 1 filament supported in said envelopeand a pinfi of reflectors supported in said envelope cmcentrically andcoaxially with respect to said filament, each of said reflectors havinga narrow light transmitting .sligsaid slits radially aligned with theaxis of said filament.

7. In a lamp, a sealed envelope, 9. filament supported in said envelope,and a pluralit of reflectors supported in said en'velo eac reflectorpartially surrounding said ament and combining with said otherreflectors to limit the light from said filament to a small dihedralangle having its vertex parallel to the axis of the filament.

8. In a lamp, a sealed envelo e, a filament supported in said envelope,a re ecting screen purposed to carry electrical currents and supportedin said envelope to partially surround said filament, and a secondreflecting screen supported in said envelo to 2:; tially surround saidfilament an said screen.

4 9. In a lamp, a sealed envelope, an incandescent body supported insaid envelope and a plurality of electrically conductive reflectorssupported by electrically conductive leading-in wires in said envelopeconcentrically and coaxially with respect to said badly, each of saidreflectors having a narrow H t transmittin slit, said slits being radia1y aligned wit an axis of said body.

10. In a lamp, a sealed envelope, an incandescent body supported insaidenvelo a conductive reflector supported in saidi envelope concentricallyand coaxially with respect to said body, leading-in wires aflixed tosaid reflector for supplying electrical ener to said reflector, a secondconductive re ector supported in said envelope to partially surroundsaid first reflector leadingin wires aflixed to said second reflectorfor supplying electrical energy to said second re ector, each of saidreflectors having a narrow light transmitting slit, .said slits-beingradially aligned with an axis of said body.

In witness whereof, we hereunto subscribe our names this 6th day of Ast, 1929.

EDMUND R. ORTON. HUGH M. STOLLER.

